Today, dental crowns of glass or glass ceramic materials are typically produced by grinding bodies of compacted and heat treated glass or glass ceramic particles.
The bodies are usually produced by mechanical compacting (e.g. uniaxial pressing) of inorganic powders often together with an organic binder first. The shape of the resulting compacted body is typically limited to the shape of the compacting tool used. Typically, cylindrical or cuboid shaped bodies are obtained.
Hereinafter, the compacted bodies usually undergo a heat treatment to increase the mechanical strength of the compacted bodies. The heat treatment typically takes place at a temperature causing a partially sintering of the powder. During such a sintering step the density of the body of compacted powder is increased to a certain extend.
The thus obtained compacted and heat treated bodies are adhesively fixed in a frame or attached to a holder and are ready for grinding to the desired shape (e.g. a dental crown or dental facing). The grinded bodies are then removed from the frame.
Machining of the compacted bodies which have not been heat treated is typically not possible due to the low mechanical strength of the compacted powder.
In contrast to using a milling process, producing dental appliances using a grinding process would be more desirable, since the wear of the machining tools is reduced and often the final dental work pieces can be produced at a higher speed. Due to the high strength of glass bodies or glass ceramic bodies, milling tools typically cannot be applied successfully and in a commercially meaningful manner.
U.S. Pat. No. 6,648,645 describes a process for fabricating a dental material comprising the steps of mixing ceramic powder and one or more media together to form a putty, applying the putty to a model to conform to the shape of the model and to form a ceramic core material and sintering the model with the putty thereon for a time of less than about 3 hours to provide a dental ceramic core material.
In view of the drawbacks described above, it would be desirable to simplify the process.